Mobile communication apparatus and method including base station and mobile station having multi-antenna

ABSTRACT

A mobile communication apparatus that utilizes multiple base station/mobile station antennas and a mobile communication method performed therein are provided. The mobile communication apparatus includes a base station having at least two antennas and at least two mobile stations having at least one antenna, respectively. The base station restores weight information and channel status information from feedback signals received from the mobile stations, determines downlink investigation information that results in maximum transmission channel capacity based on the restored weight information and channel status information, selects mobile stations for simultaneous transmission based on the downlink investigation information, and processes data to be transmitted to the selected mobile stations based on the downlink investigation information.

PRIORITY

This application is a Divisional Application U.S. application Ser. No.11/504,798, filed Aug. 15, 2006, which is a Continuation of U.S.application Ser. No. 10/531,638, filed on Apr. 15, 2005, which claimspriority under 35 U.S.C. 119 to an application entitled “MobileCommunication Apparatus and Method Including Base Station and MobileStation Having Multi-Antenna” filed in the Korean Intellectual PropertyOffice on Oct. 19, 2002 and assigned Serial No. 2002-64009, the contentsof all of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to mobile communications, and moreparticularly, to a mobile communication apparatus includingmulti-antenna base station and mobile stations, which maximizesthroughput in a multi-user communication environment based on high-speeddownlink wireless packet access, and a mobile communication methodtherefor.

2. Description of the Related Art

Various technologies are used to maximize throughput in mobilecommunications. As such, logical improvements using new wireless accessand physical improvements using, for example, multiple antennas, haveattracted more attention than other methods.

First, as an example of a new wireless access based logical improvementmethod, next-generation mobile communication system standardizationassociations have proposed in recent years new standard packet accesstechnologies enabling high-speed packet transmission via downlinks. The3^(rd) Generation Partnership Project (3GPP), an asynchronousstandardization association led by Europe and Japan, works for thestandardization of high-speed downlink packet access (HSDPA) technology,and the 3GPP2, a synchronous standardization association led by the U.S.works for the standardization of 1× Evolution Data Only/Voice (1×EV-DON)technology. The HSDPA and 1×EV-DON technologies suitable for web-basedInternet services are based on high-speed downlink packet access forwireless packet transmission. Since high-speed downlink packet access isoptimized for peak throughput as well as average throughput, it canachieve peak throughput in an intermittent wireless packet transmissionenvironment. The implementation of such a high-speed downlink packetaccess technology basically requires an adaptive modulation & coding(AMC) technology, a hybrid automatic request (HARQ) technology, and amulti-user diversity scheduling technology. Basic technologies fordownlink packet access are described in the 3GPP specification, aEuropean IMT-2000 standard, and the article “CDMA/HDR: A BandwidthEfficient High Speed Wireless Data Service for Nomadic Users” by P.Bender, P. Black, M. Grob, R. Padovani, N. Sindhushayana, and A.Viterbi, IEEE Communications, Vol. 38(7), 70-78, July, 2000.

Second, unlike the wireless access improvement method enabling theefficient use of bandwidths within a given range, a physical improvementmethod using multiple antennas increases bandwidth resources using morespatial resources to maximize throughput. Recently, Lucent Technologiesverified through intensive research into BLAST (Bell Labs LAyered SpaceTime) demonstrated that the bandwidth is increased min(N,M) times whenusing N base station antennas and M mobile station antennas compared towhen using a single base station antenna and a single mobile stationantenna. Here, min(N,M) means the minimum of N and M. This researchensured the effectiveness of using multiple antennas for peakthroughput. The principle of increasing the channel capacity usingmultiples antennas in a base station and mobile stations can beexplained based on a matrix rank criterion. The number of paths isdetermined by the rank characteristic of the matrix H of channeldownlink characteristics of multiple base station and mobile stationantennas. A rich scatter environment for mobile communications can becreated by a number of uncritical obstacles. In such a rich scattercommunication environment, the theoretical maximum capacity C_(MAX) of amulti-antenna communication system including a base station and a singlemobile station is expressed as equation (1) below based on Shannon'schannel capacity bound principle. $\begin{matrix}{C_{MAX} = {\log_{2}{\det\left\lbrack {I + {\frac{1}{\sigma_{n}^{2}}H^{H}{PH}}} \right\rbrack}}} & (1)\end{matrix}$where I denotes an identity matrix, P denotes a diagonal matrix of powerallocation parameters, and σ_(n) ² denotes the variance of noise.Shannon's channel capacity bound principle and Lucent's BLAST technologyare described in the article entitled “On Limits of WirelessCommunications in a Fading Environment When Using Multiple Antennas,” byG. J Foschini and M. J. Gans, Wireless Personal Communications, Vol. 6,pp. 311-335, August 1998.

In particular, Lucent's BLAST technology provides maximum channelcapacity based on equation (1) in an environment where one base stationcorresponds to one mobile station. Since the BLAST technology does notrequire channel information feedback, problems such as delay orerroneous fed-back do not arise. However, in a multi-antenna systembased on Lucent's BLAST technology, in which data is transmitted viaonly one channel between the base station and a mobile station, and nochannel information is fed back, it is impossible to apply a nullingmethod, which forms a principle of multi-antenna systems, and to achievepeak throughput in a multi-user, multi-antenna system environment. Inaddition, there is a structural limitation in that more mobile stationantennas than base station antennas are required. The concept of thenulling principle for multi-antenna systems is described in the articleentitled “Applications of Antenna Arrays to Mobile Communications, PartI: Performance Improvement, Feasibility, and System Considerations,” byLAL C. GODARA, Proceedings of the IEEE, Vol. 85, No. 7, 1031-1097, July1997 (refer to D. Null Beamforming on page 1041).

In the above-described physical improvement method using multipleantennas, channel information cannot be fed back to achieve peakthroughput in a low-speed Doppler environment including low-speed mobilestations, in which channel switching rarely occurs, or in a high-powerenvironment ensuring minimal channel feedback errors. The problem oflower throughput is considered to be more serious because informationfed back from a plurality of mobile stations cannot be simultaneouslyconsidered.

To solve the problem of the above-described method that information fedback from a plurality of mobile stations cannot be simultaneouslyinterpreted, there are required the following considerations: (1)separating channel investigation and tracking sections for adaptation toa high-speed Doppler channel environment, (2) how to handle a pluralityof mobile stations having unfair packets, (3) quantization using spatialweighting factors for efficient channel information measurement, and (4)compatibility with existing standards. However, it has never beenconsidered so far to generate channel information based on the currentlyavailable weight information and channel status information, ratherusing new channel information, to achieve maximum channel throughput.

SUMMARY OF THE INVENTION

The present invention provides a mobile communication apparatusincluding a base station with at least two base station antennas and atleast two mobile stations each of which has at least one antenna. In themobile communication apparatus, the downlink characteristics of spatialchannels between the base station and at least two mobile stations areconsidered with respect to every mobile station, thereby solving aproblem of delay in optimal beamforming by the base station antenna andin multi-stream data transmission. In addition, according to the presentinvention, user fairness in data transmission is also considered, andchannel information is measured in an easier way, ensuring the nominalthroughput for multi-user, multi-antenna systems.

The present invention also provides a mobile communication methodperformed in the above mobile communication apparatus that includemultiple base station and mobile station antennas.

In an aspect of the present invention, there is provided a mobilecommunication apparatus with multiple base station/mobile stationantennas, the apparatus including a base station and at least two mobilestations, comprising: the base station restoring weight information andchannel status information from feedback signals received from themobile stations, determining downlink investigation information thatresults in maximum transmission channel capacity based on the restoredweight information and channel status information, selecting mobilestations for simultaneous transmission from among all of the mobilestations based on the downlink investigation information, and processingdata to be transmitted to the selected mobile stations based on thedownlink investigation information, wherein the base station includes atleast two base station antennas and each of the mobile stations includesat least one mobile station antenna.

In another aspect of the present invention, there is provided a mobilecommunication apparatus with multiple base station/mobile stationantennas, the apparatus including a base station and at least two mobilestations, comprising: the base station restoring weight information andchannel status information from feedback signals received from themobile stations, determining downlink investigation information thatresults in maximum transmission channel capacity based on the restoredweight information and channel status information, selecting mobilestations for simultaneous transmission from among all of the mobilestations based on the downlink investigation information, determiningdownlink tracking information based on the channel downlinkinvestigation information and restored weight information and channelstatus information regarding the selected mobile stations, andprocessing data to be transmitted to the selected mobile stations basedon the downlink tracking information, wherein the base station includesat least two base station antennas and each of the mobile stationsincludes at least one mobile station antenna.

In another aspect of the present invention, there is provided a methodof mobile communications between a base station and at least two mobilestations, wherein the base station includes at least two base stationantennas, and each of the mobile stations includes at least one mobilestation antenna, the method comprising (a) the base station restoringweight information and channel status information from feedback signalsreceived from the mobile stations, determining downlink investigationinformation that results in maximum transmission channel capacity basedon the restored weight information and channel status information,selecting mobile stations for simultaneous transmission from among allof the mobile stations based on the downlink investigation information,and processing data to be transmitted to the selected mobile stationsbased on the downlink investigation information.

In another aspect of the present invention, there is provided a methodof mobile communications between a base station and at least two mobilestations, wherein the base station includes at least two base stationantennas, and each of the mobile stations includes at least one mobilestation antenna, the method comprising (a) the base station restoringweight information and channel status information from feedback signalsreceived from the mobile stations, determining downlink investigationinformation that results in maximum transmission channel capacity basedon the restored weight information and channel status information,selecting mobile stations for simultaneous transmission from among allof the mobile stations based on the downlink investigation information,determining downlink tracking information based on the channel downlinkinvestigation information and restored weight information and channelstatus information regarding the selected mobile stations, andprocessing data to be transmitted to the selected mobile stations basedon the downlink tracking information.

The method further comprises (b) each of the mobile stations measuringdownlink characteristics of multiple base station/mobile station antennachannels based on pilot channel signals transmitted from the basestation, determining the weight information and channel statusinformation based on the downlink characteristics, converting thedetermined weight information and channel status information into thefeedback signals, transmitting the feedback signals to the base station,and detecting high-speed downlink shared channel (HS-DSCH) signals inunits of a frame based on the downlink characteristics, and a firstcontrol signal and data signals, which are transmitted from the basestation.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and advantages of the present inventionwill become more apparent by describing in detail exemplary embodimentsthereof with reference to the attached drawings in which:

FIG. 1 is a block diagram of a mobile communication apparatus accordingto the present invention;

FIG. 2 is a flowchart of a mobile communication method according to thepresent invention performed in the mobile communication apparatus inFIG. 1;

FIG. 3 is a flowchart of an embodiment of step 21 in FIG. 2 according tothe present invention;

FIG. 4 is a block diagram of an embodiment of a first, second, . . . ,or K^(th) mobile station in FIG. 1 according to the present invention;

FIG. 5 is a flowchart of an embodiment of step 23 in FIG. 2 according tothe present invention;

FIG. 6 is a block diagram of a base station in FIG. 1;

FIG. 7 is a flowchart of step 52 in FIG. 5 according to the presentinvention;

FIG. 8 is a block diagram of an embodiment of a downlink investigationinformation generation unit in FIG. 6 according to the presentinvention;

FIG. 9 is a flowchart of step 53 in FIG. 5; and

FIG. 10 is a block diagram of a downlink tracking information generationunit in FIG. 6.

DETAILED DESCRIPTION OF AN EXEMPLARY EMBODIMENT

The structure and operation of a mobile communication apparatus thatutilizes multiple base station and mobile station antennas, and a mobilecommunication method therefor according to the present invention will bedescribed in detail with reference to the appended drawings.

As shown in FIG. 1, which is a block diagram of a mobile communicationapparatus according to an embodiment of the present invention, themobile communication apparatus includes a base station 11, a firstmobile station 13, a second mobile station 15 through a K^(th) mobilestation 17. Each of the K mobile stations, where K is an integer of 2 orgreater, performs the same function. According to the present invention,the number of mobile station antennas, M(k_(u)), in each of the mobilestations 13 through 17 may be greater than 1 and smaller than the numberof base station antennas, B, in the base station 111, i.e.,1≦M(k_(u))≦B. The number of mobile station antennas M(k_(u)) may begreater than or equal to the number of base station antennas B, i.e.,M(k_(u))≧B. M(k_(y)) is a positive integer that is greater than or equalto 1, B is a positive integer that is greater than or equal to 2, andk_(u) denotes mobile station's ID number, where 1≦k_(u)≦K.

FIG. 2 is a flowchart illustrating a mobile communication methodaccording to an embodiment of the present invention performed in themobile communication apparatus in FIG. 1. The mobile communicationmethod includes determining and transmitting weight information andchannel status information and detecting high-speed downlink sharedchannel (HS-DSCH) signals (step 21) and adding pilot channel (PICH)signals to data signals generated based on the weight information andchannel status information restored from feedback signals andtransmitting the added results (step 23).

Step 23 in FIG. 2 that is performed in the base station 11 will now bedescribed prior to a description on step 21.

The base station 11 restores the weight information and channel statusinformation determined in each of the first through K^(th) mobilestations 13 through 17 from the feedback signals received from each ofthe first through K¹¹ mobile stations 13 through 17 based on the channeldownlink characteristics of the multiple base station and mobile stationantennas (hereinafter, referred to as first characteristics H(k_(u)),where H(k_(u)) is a matrix with 1≦k_(u)≦K). Hereinafter, capital boldletters indicate matrices, small bold letters indicate vectors, andnon-bold symbols indicate scalars. The base station 11 also generatesdownlink investigation information that ensures maximum throughput basedon the restored weight information and channel status informationregarding each of the mobile stations. The maximum throughput may becalculated in consideration of transmission packet fairness information.The base station 11 selects data regarding mobile stations forsimultaneous transmission from among data regarding all of the mobilestations based on the generated downlink investigation information. Thebase station 11 generates downlink tracking information appropriate toinstant channel situations based on feedback signals received from themobile stations selected for simultaneous transmission. The base station11 matrix-multiplies the data regarding the selected mobile stations bythe downlink tracking information that is mutual weight information,adds mobile station selection information and pilot channel signalsPICHi to the products (also referred to as data signals) of themultiplication, and transmits the added results to the first throughK^(th) mobile stations 13 through 17 in units of a frame.

The downlink investigation information includes mobile station selectioninformation described later, i.e., information regarding mobile stationsto which data will be concurrently transmitted. The firstcharacteristics H(k_(u)) means the phase and magnitude of channelsthrough which data are transmitted from the base station 11 to arbitrarymobile stations 13 through 17.

The first characteristics H(k_(u)) that is a matrix consisted of basestation antenna channels in columns and mobile station antenna channelsin rows. In other words, the column components of the firstcharacteristics matrix H(k_(u)) are derived from the space formed by thebase station antennas, and the row components thereof are derived fromthe space formed by the mobile station antenna. The pilot channelsignals PICH_(i) may be common pilot channel (CPICH) signals, dedicatedcommon pilot channel (DCPICH) signals, secondary common pilot channel(SCPICH) signals, etc.

In another embodiment of the base station 11, instead of generating thedownlink tracking information, mutual weight information contained inthe downlink investigation information may be matrix-multiplied by thedata regarding the selected mobile stations.

The first through K^(th) mobile stations 13 through 17 may beimplemented in any structure provided that they ensures the base station11 to perform the above operations and that they can determine theweight information and channel status information based on the firstcharacteristics H(k_(u)). Step 21 in FIG. 2 performed in the firstthrough K^(th) mobile stations 13 through 17 will now be described.

Each of the first through K′h mobile stations 13 through 17 measures thefirst characteristics H(k_(u)) based on the PICH signals transmittedfrom the base station 11 and determines based on the measured firstcharacteristics H(k_(u)) the weight information and channel statusinformation that ensure peak throughout to each of the channelsconnecting the base station and mobile station antennas. Each of thefirst through K^(th) mobile stations 13 through 17 converts thedetermined weight information and channel status information intofeedback signals and transmits them to the base station 11. Each of thefirst through K^(th) mobile stations 13 through 17 generates ahigh-speed downlink shared channel (HS-DSCH) signal in units of a framebased on the first characteristics H(k_(u)), and a first control signaland data signals, which are received from the base station 11.

Each of the first through K^(th) mobile stations 13 through 17 analysesthe first control signal received through the mobile station antennas todetermine whether a signal transmitted from the base station 11 iscorrectly addressed thereto. The HS-DSCH signal reflects the second andthird characteristics of channels. The second characteristics imply thatthe transmission of data through a channel is completed withoutrequiring channel switching because the length of a data frame, i.e.,the unit of data transmission, is much shorter than the coherence timeof a general Doppler channel. The third characteristics are related tothe non-continuous, burst transmission of data through a channelcommonly owned by all of the mobile stations 13 through 17 belonging tothe base station 11.

For the convenience of understanding the present invention, embodimentsof the first, second through K^(th) mobile station 13 through 17 in FIG.1 and step 21 will be described first, followed by descriptions onembodiments of the base station 11 and step 23.

FIG. 3 is a flowchart illustrating an embodiment of step 21 in FIG. 2according to the present invention, which includes transmitting theweight information and channel status information determined based onthe first characteristics H(k) to the base station 11 (steps 31 through33) and selecting and combining desired data information from among datainformation restored based on the data signals transmitted from the basestation 11 (steps 34 through 37).

FIG. 4 is a block diagram of an embodiment of the first through K^(th)mobile station 13 through 17 in FIG. 1, which includes an antenna array41, a channel characteristics measurement unit 42, a channel informationdetermination unit 43, an information feedback unit 44, a controlinformation restoration unit 45, a data information restoration unit 46,a data information selection unit 47, and a data information combinationunit 48.

The operation of the first, second through K^(th) mobile station 13through 17 having the structure of FIG. 4 will be described inconnection with the flowchart of FIG. 3.

In particular, the antenna array 41 in FIG. 4 includes M(k_(u)) mobileantennas 41 a through 41 c. The antenna array 41 receives the PICHsignals, the data signals, and the first control signal transmitted fromthe base station 11. The channel characteristics measurement unit 42measures the first characteristics H(k_(u)) based on the PICH signalsreceived via the antenna array 41 from the base station 11 and outputsthe measured first characteristics H(k_(u)) to the channel informationdetermination unit 43, the control information restoration unit 45, andthe data information restoration unit 46 (step 31).

The channel information determination unit 43 determines the weightinformation V(k_(u)) and channel status information Λ(k_(u)) thatmaximize throughput based on the first characteristics H(k_(u)), whichhave been compressed to be fed back, and outputs the determined weightinformation V(k_(u)) and channel status information Λ(k_(u)) to theinformation feedback unit 44 (step 32). The weight information V(k_(u))and channel status information Λ(k_(u)) are determined by decomposingthe first characteristics H(k_(u)) into U(k_(u))Λ(k_(u))V^(H)(k_(u))using a singular value decomposition method.

N_(B)(k_(u)) is smaller than or equal to B and grater than or equal to1, and the number of vectors and the number of gain values in a basismatrix are both smaller than or equal to B. This is conceptually thesame as when some gain values become null depending on the firstcharacteristics H(k_(u)), which are the downlink channel characteristicsof the base station/mobile station antennas. In both the cases, thenumber of vectors in the basis matrix and the number of gain values maybe expressed as N_(B)(k_(u)).

The information feedback unit 44 converts the weight informationV(k_(u)) and channel status information Λ(k_(u)) received from thechannel information determination unit 43 into feedback signals that aresuitable to be fed back to the base station 11 using a generalcommunication signal processing technique and transmits the convertedfeedback signals via the mobile station antenna array 41 to the basestation 11 (step 33). To perform step 33, the information feedback unit44 may format the weight information V(k_(u)) and channel statusinformation Λ(k_(u)) received from the channel information determinationunit 43, time-division-multiplex the formatted results, and transmit thetime-division-multiplexed results as the feedback signals via the mobilestation antenna array 41 to the base station 11. Alternatively, theinformation feedback unit 44 may apply code division multiplexing orfrequency division multiplexing, instead of time division multiplexing,to the formatted weight information V(k_(u)) and channel statusinformation Λ(k_(u)) to generate the feedback signals.

The control information restoration unit 45 compensates for a distortionof the first control signal, which has been received through the mobilestation antenna array 41 from the base station 11, using the firstcharacteristics H(k_(u)) input from the channel characteristicsmeasurement unit 42, restores a second control signal from thedistortion-compensated first control signal, and outputs the restoredsecond control signal to the data information selection unit 80 (step34). The second control signal includes information as to whether thedata signals received by the mobile station are assigned thereto andinformation on a basis from which the mobile station receives the datasignals. The second control signal may be restored from the firstcontrol signal using a general multi-antennal signal process, which willbe also used in step 35 described later.

The data information restoration unit 46 restores data information thatis received from all bases from the data signals received through themobile station antenna array 41 from the base station 11 and the firstcharacteristics H(k_(u)) input from the channel characteristicsmeasurement unit 42 and outputs the restored data information to thedata information selection unit 47 (step 35). The data signals receivedfrom the base station 11 are expressed as r(k) in equation (2) below andcan be modelled using equation (3) below.r(k)=[r(l,k)r(2,k) . . . r(N,k)]^(T)  (2)where r(n,k) denotes a data signal received via an n^(th) antenna of theK^(th) mobile station.r(k)=H(k)x+n(k)=U(k)Λ(k)V ^(H)(k)x+n(k)  (3)where n(k) denotes a noise component, and U(k)Λ(k)V^(H)(k) is the resultof singular value decomposition (SVD), which is a general matrixoperation, on the first characteristics H(k_(u)), and x is modelled asin equation (4) below. SVD in multi-antenna systems is described in anarticle entitled “Fading Correlation and Its effect on the Capacity ofMultielement Antenna Systems” by Da-Shian Shiu, Gerard J Foschiini,Michael J. Gans, and Josep M. Kahn, IEEE Transactions on Comm. Vol. 48,No. 3, 502-513, March 2003.x=Wd  (4)where W is an optimal basis matrix generated in the base station 11 andd denotes data information.

Referring back to FIGS. 3 and 4, the data information selection unit 47selects data information which is received from a desired basis amongthe data information from every basis, which is received from the datainformation restoration unit 46, in response to the second controlsignal, and outputs N_(e)(k) data information values received from thedesired basis, where 0≦N_(e)(i)≦N, to the data information combinationunit 48 (step 36).

The data information combination unit 48 combines the selected datainformation values output from the data information selection unit 47over a predetermined period of time T_(BLOCK) that corresponds to thelength of a frame, and outputs the combined result as a high-speeddownlink shared channel signal HS-DSCH(i)′ of the corresponding mobilestation (step 37).

Unlike the step 21 illustrated in FIG. 3, steps 34 and 37 may beperformed while steps 32 and 33 are performed. Alternatively, steps 34through 37 may precede steps 32 and 33.

Operations of the base station 11 in FIG. 1 and step 23 in FIG. 2according to the present invention will now be described with referenceto FIGS. 5 and 6.

FIG. 5 is a flowchart illustrating step 23 in FIG. 2 according to thepresent invention, which includes generating the downlink investigationinformation and downlink tracking information based on the restoredweight information and channel status information (steps 51 through 53),selecting data regarding desired mobile stations (step 54), processingthe selected data based on the downlink tracking information to generatedata signals (step 55), and adding mobile station selection informationcontained in the downlink investigation information, and pilot channelsignals to the data signals and transmitting the added results to thecorresponding mobile station (step 56).

In step 23, step 53 may be not performed. In other words, step 23 mayinclude generating the downlink investigation information based on therestored weight information and channel status information (steps 51 and52), selecting data regarding desired mobile stations (step 54),processing the selected data based on the mutual weight informationcontained in the downlink investigation information to generate datasignals (step 55), adding mobile station selection information containedin the downlink investigation information, and pilot channel signals tothe data signals, and transmitting the added results to thecorresponding mobile station (step 56).

In step 23 in FIG. 5, when generating the downlink investigationinformation in step 52 in each of the above embodiments, mobile stationfairness information, i.e., packet fairness information between mobilestations, may be further considered.

FIG. 6 is a block diagram of an operation of the base station 1 in FIG.1 according to the present invention. As illustrated in FIG. 6, the basestation 11 may include an antenna array 61, a feedback informationrestoration unit 62, a decomposition unit 63, a mobile station fairnesscontrol unit 64, a downlink investigation information generation unit65, a downlink tracking information generation unit 66, a mobile stationdata selection unit 67, a basis multiplication unit 68, and an additionunit 69. The mobile station fairness control unit 64 is optional.

The operation of the base station 11 in FIG. 6 will be described inconnection with the flowchart of FIG. 5.

In FIG. 6, the antenna array 61 includes N base station antennas 61 athrough 61 c. The antenna array 61 receives the feedback signalscontained in uplink dedicated physical control channel signals(HS-DPCCH) that are transmitted from the first through K^(th) mobilestations 13 through 17 and transmits the results of adding the mobilestation selection information and pilot channel signals to data signals,which are spatially processed HS-DSCH signals, to the first throughK^(th) mobile stations 13 through 17.

The feedback information restoration unit 62 restores the weightinformation V(k_(u)) and channel status information Λ(k_(u)) from thefeedback signals received through the base station antenna array 61 fromthe first through K^(th) mobile stations 13 through 17 and outputs therestored weight information V(k_(u)) and channel status informationΛ(k_(u)) to the decomposition unit 63.

The decomposition unit 63 decomposes the weight information V(k_(u)) andchannel status information Λ(k_(u)), which are matrices, into weightvectors v(k) and channel status vectors λ(k) and outputs the decomposedweight vectors v(k) and channel status vectors λ(k) to the downlinkinvestigation information generation unit 65 and the downlink trackinginformation generation unit 66 (step 51). The restored weight vectorsV(k_(u)) for the individual mobile stations are expressed asV(k_(u))={v₁, v₂, . . . , v_(K)}, and the restored channel statusinformation λ(k_(u)) for the individual mobile stations are expressed asλ(k_(u))={λ₁, λ₂, . . . , λ_(K)}.

In a case where the information feedback unit 44 in FIG. 4 has generatedthe feedback signals using time division multiplexing, the feedbackinformation restoration unit 62 restores the weight information V(k_(u))and channel status information Λ(k_(u)) using time divisiondemultiplexing. In a case where the information feedback unit 44 hasgenerated the feedback signals using code division multiplexing orfrequency division multiplexing, instead of time division multiplexing,the feedback information restoration unit 62 restores the weightinformation V(k_(u)) and channel status information Λ(k_(u)) using codedivision demultiplexing or frequency division demultiplexing.

The mobile station fairness control unit 64 generates mobile stationfairness information {t_(k)} regarding the individual mobile stationsand outputs the mobile station fairness information {t_(k)} to thedownlink investigation information generation unit 65. The mobilestation fairness information {t_(k)} may be generated in considerationof maximum transmission channel capacity C_(MAX). The mobile stationfairness information {t_(k)} consists of packet fairness informationregarding each of the mobile stations, which is expressed as{t_(k)}={t₁, t₂, . . . , t_(K)}. A technique of generating the mobilestation fairness information {t_(k)} is disclosed by Paramod Viswanath,David N. C. Tse, and Rajiv Laroia in an article entitled “OpportunisticBeamforming Using Dumb Antennas”, IEEE Transactions on InformationTheory, Vol. 48, No. 6, page 1277-1294.

In an investigation section prior to packet transmission to the mobilestations, the downlink investigation information generation unit 65generates downlink investigation information based on the restoredweight vectors v(k) and channel status vectors λ(k) input from thefeedback information restoration unit 62 and the mobile station fairnessinformation {t_(k)} input from the mobile station fairness control unit62, and outputs maximum index information i_(MAX), which is mobilestation selection information contained in the downlink investigationinformation, to the downlink tracking information generation unit 66,the mobile station data selection unit 67, and the addition unit 69(step 52). The maximum index information i_(MAX) consists of i_(USER)(1)through i_(USER)(N_(B)). The maximum transmission channel capacityinformation C_(MAX) contained in the downlink investigation informationis provided to the mobile station fairness control unit 64.

In a tracking section for packet transmission to the mobile stations,the downlink tracking information generation unit 66 generates mutualweight information W based on the restored weight vectors and channelstatus vectors input from the feedback information restoration unit 62and the maximum index information i_(MAX), which is mobile stationselection information contained in the downlink investigationinformation, input from the downlink investigation informationgeneration unit 65, and outputs the generated mutual weight informationW to the basis multiplication unit 68 (step 53).

The mobile station data selection unit 67 selects packet channelsconnected to the mobile stations selected for data transmission, fromamong the packet channels HS-DSCH(k) for all of the mobile stations, inresponse to the maximum index information i_(MAX) that is mobile stationselection information input from the downlink investigation informationgeneration unit 65, and outputs the packet channels connected to theselected mobile stations to the basis multiplication unit 68 (step 54).

The basis multiplication unit 68 performs matrix-multiplicationoperation on a set of mutual weight information {W} output from thedownlink tracking information generation unit 66 and data regarding Nmobile stations selected by the mobile station data selection unit 67and outputs the results of the matrix-multiplication to the additionunit 69 as data signals (step 55). Matrix-multiplication includesmultiplying the mutual weight information W by the data regarding Nmobile stations selected by the mobile station data selection unit 67and summing all of the products.

The addition unit 69 adds externally input pilot channel signals PICH₁through PICH_(N) to the data signals input from the basis multiplicationunit 68 and outputs the added results to the base station antenna array61 (step 56). To this end, the addition unit 69 is implemented withfirst through N^(th) adders (not shown). An N^(th) adder (not shown)adds a pilot channel signal PICH_(n) to a data signal input from thebasis multiplication unit 68 and outputs the added result to acorresponding antenna 61 a through 61 c in the base station antennaarray 61. The added result input to the base station antenna array 61from the addition unit 69 is transmitted to the mobile stations 13through 17 in units of a frame.

In another embodiment of the base station 11, the downlink trackinginformation generation unit 66 described above may be excluded. In thiscase, in an investigation section prior to packet transmission to themobile stations, the downlink investigation information generation unit65 generates downlink investigation information based on the restoredweight vectors v(k) and channel status vectors λ(k) input from thefeedback information restoration unit 62 and the mobile station fairnessinformation {t_(k)} input from the mobile station fairness control unit62. The maximum index information i_(MAX), which is mobile stationselection information contained in the downlink investigationinformation, is output to the mobile station data selection unit 67 andthe addition unit 69. The maximum transmission channel capacityinformation C_(MAX) contained in the downlink investigation informationis output to the mobile station fairness control unit 64. The mutualweight information W_(MAX) contained downlink investigation informationis output to the basis multiplication unit 68. As in the precedingembodiment, the mobile station fairness control unit 64 is optional.

Operations of Step 52 in FIG. 5 and the downlink investigationinformation generation unit 65 in FIG. 6 according to the presentinvention will be described with reference to FIGS. 7 and 8.

FIG. 7 is a flowchart illustrating an operation of step 52 in FIG. 5,which includes generating downlink investigation information based onthe restored weight information and channel status information and themobile station fairness information (steps 71 through 79). In anotherembodiment, the downlink investigation information may be generatedbased on only the restored weight information and channel statusinformation.

FIG. 8 is a block diagram illustrating the structure of the downlinkinvestigation information generation unit 65 of FIG. 6 according to anembodiment of the present invention, which includes a multiplicationportion 810, a sub-part combination portion 820, a mutual weightinformation generation portion 830, a channel capacity calculationportion 840, a storage portion 850, an index setting portion 860, and amaximum values search portion 870. The sub-part combination portion 820may be implemented with a channel information sub-part combinationportion 820 and a mobile station fairness information sub-partcombination portion 822. Alternatively, the sub-part combination portion820 may be implemented with the channel information sub-part combinationportion 820 alone. The index setting portion 860 may be implemented witha delay 861 and a counter 862.

The operation of the downlink investigation information generation unit65 in FIG. 8 will be described with reference to the flowchart in FIG.7.

The multiplication portion 810 multiplies the weight information vector{v(k)} by the channel status information vector {Λ(k)}, as expressed inequation (5), and outputs the product {h_(k)} to the channel informationsub-part combination portion 821 of the sub-part combination unit 820(step 71). If the available channel capacity (log₂ (1+λ(k))/t_(k)) of amobile station, which is a ratio of the channel capacity (log₂ (+Λ(k)))converted from the corresponding channel status information vector λ(k)to the corresponding mobile station fairness information t_(k), issmaller than a predetermined threshold value, data transmission to themobile station is improbable. Therefore, it is unnecessary to performmultiplication itself for such mobile stations.h _(k)=λ(k)*v(k)  (5)

The counter 862 in the index setting portion 860 increases the index (i)one by one, wherein the index (i) is initialized to 1 (step 72). Theindex (i) indicates the number of all possible combinations of the firstthrough K^(th) mobile stations 13 through 17. The maximum value of theindex (i) is _(k)C_(min(K,N)).

The channel information sub-part combination portion 821 of the sub-partcombination unit 820 combines the product {h_(k)} output from themultiplication portion 810 into sub-parts as expressed in equation (6)with reference to the index (i) provided by the counter 861 and outputsthe combined result H_(s) to the mutual weight information generationunit 830. The mobile station fairness information sub-part combinationportion 822 combines the mobility station fairness information {t_(k)}into sub-parts for the individual mobile stations as expressed inequation (7) and outputs the combined result T_(s) to the channelcapacity calculation unit 840 (step 73).H _(s) =[h _(k(1)) h _(k(2)) . . . h _(k(N) _(B) ₎ ], k(n _(B))ε{1, 2, .. . , K}  (6)T _(s) =[t _(k(1)) t _(k(2)) . . . t _(k(N) _(B) ₎ ], k(n _(B))ε{1, 2, .. . , K}  (7)

The mutual weight information generation unit 830 generates the floatpoint mutual weight information W based on the combined result H_(s)received from the channel information sub-part combination portion 821using equation (8) and outputs the generated mutual weight information Wto the channel capacity calculation portion 840 (step 74). To make iteasier to measure the channel information, the mutual weight informationW may be quantized to a degree that is suitable to be fed back and thenoutput to the channel capacity calculation portion 840.W=H _(s) ^(H)(H _(s) H _(s) ^(H) +N _(o) /E _(b))⁺  (8)

The channel capacity calculation portion 840 calculates the transmissionchannel capacity C based on the result of combining the channelinformation, H_(s), and the result of combining the mobile stationfairness information, T_(s), which are received from the sub-partcombination unit 820, and the mutual weight information W received fromthe mutual weight information generation portion 830 using equation (9)below, and outputs the calculated transmission channel capacity C to thestorage portion 850 (step 75). $\begin{matrix}{C = {\sum\limits_{n_{B} = 1}^{N_{B}}{\frac{1}{t_{k{(n_{B})}}}{\log_{2}\left( {1 + \frac{E_{b}{{w_{n_{B}}^{H}h_{k{(n_{B})}}}}}{{E_{b}{\sum\limits_{{n = 1},{n \neq n_{B}}}^{N_{B}}{{w_{n}^{H}h_{k{(n_{B})}}}}}} + N_{a}}} \right)}}}} & (9)\end{matrix}$where W=[w₁, w₂, . . . , w_(N) _(B) ].

Alternatively, the mobile station fairness information may be notconsidered by substituting the term t_(k) in equation (9) with unity.

The storage portion 850 stores the transmission channel capacity Coutput from the channel capacity calculation portion 840, the mutualweight information W output from the mutual weight informationgeneration unit 830, and the index (i) output from the counter 862 tillthe index (i) input from the counter 862 is not greater than$\sum\limits_{n_{B} = 1}^{\min{({K,N})}}{{}_{}^{}{}_{nB}^{}}$(step 76).

The storage portion 850 determines whether the index (i) received fromthe counter 862 is greater than$\sum\limits_{n_{B} = 1}^{\min{({K,N})}}{{}_{}^{}{}_{nB}^{}}$(step 77). If the currently received index (i) is determined to begreater than${\sum\limits_{n_{B} = 1}^{\min{({K,N})}}{{}_{}^{}{}_{nB}^{}}},$the storage portion 850 outputs a set of the indices {i} from the firstindex, i.e., unity, to the last index just preceding the currentreceived index (i), the transmission channel capacity {C}, and themutual weight information {W} to the maximum values search portion 870.The storage portion 850 outputs to the delay 861 a signal that instructsthe counter 862 to increase the index (i) by one. The delay 861 delaysthe instruction signal for a predetermined clock period and outputs thedelayed instruction signal to the counter 862.

The counter 862 increases the index (i) by one in response to the indexincreasing signal and outputs the increased index to the sub-partcombination unit 820 and the storage portion 850 (step 78).

If the index (i) received from the counter 862 is greater than${\sum\limits_{n_{B} = 1}^{\min{({K,N})}}{{}_{}^{}{}_{nB}^{}}},$the maximum values search unit 870 searches input data values i_(MAX),C_(MAX), and W_(MAX) that result in maximum transmission channelcapacity C in response to the input index {i} among the calculatedtransmission channel capacities for all possible combinations of thefirst through K^(th) mobile stations 13 through 17 and outputs thesearched input data values i_(MAX), C_(MAX), and W_(MAX) (step 79). Themaximum index value IMAX that is a kind of mobile station selectioninformation output from the maximum values search unit 870 is output tothe downlink tracking information generation unit 65, the mobile stationdata selection unit 66, and the addition unit 68. Also, the maximumtransmission channel capacity C_(MAX) and the mutual weight informationW_(MAX) are transmitted to relevant upper layers.

Operations of step 53 in FIG. 5 and the downlink tracking informationgeneration unit 66 in FIG. 6 according to the present invention will bedescribed with reference to FIGS. 9 and 10.

FIG. 9 is a flowchart of an operation of step 53 in FIG. 5 according tothe present invention, which includes generating mutual weightinformation based on the restored weight vector {v(k)}, channel statusvector {λ(k)}, and mobile station selection information i_(MAX)contained in the downlink investigation information (steps 91 through93).

FIG. 10 is a block diagram of an operation of the downlink trackinginformation generation unit 66 in FIG. 6 according to the presentinvention. The downlink tracking information generation unit 66 of FIG.10 includes a channel information sub-part selection portion 101, amultiplication portion 104, and a mutual weight information generationportion 105. The channel information sub-part selection portion 101includes a weight information sub-part selection portion 102 and achannel status information sub-part selection portion 103.

The operation of the downlink tracking information generation unit 66 inFIG. 10 will now be described in connection with the flowchart of FIG.9.

The weight information sub-part selection portion 102 and the channelstatus information sub-part selection portion 103 in the channelinformation sub-part selection portion 101 select weight information andchannel status information regarding the mobile stations that match themaximum index i_(MAX) input from the downlink investigation informationgeneration unit 65, from among the restored weight information andchannel status information input from the feedback informationrestoration unit 62, respectively, and outputs the selected weightinformation and channel status information, respectively, to themultiplication portion 104 (step 91).

The multiplication portion 104 multiplies the weight information andchannel status information input from the channel information sub-partselection portion 101, as expressed in formula (5) above, and outputsthe product h_(k), where k=i_(MAX), to the mutual weight informationgeneration portion 105 (step 92).

The mutual weight information generation portion 104 generates the floatpoint mutual weight information based on the product ht, wherek=i_(MAX), input from the multiplication unit 104 using equation (8)above and outputs the generated mutual weight information W to the basismultiplication unit 68 (step 93). To make it easier to measure thechannel information, the generated mutual weight information may bequantized to a degree that is suitable to be fed back prior to beingoutput to the basis multiplication unit 67.

As described above, in a mobile communication apparatus using multiplebase station and mobile station antennas and a mobile communicationmethod used therein according to the present invention, downlinkcharacteristics information transmitted from every mobile station to thebase station is considered to achieve optimal beamforming and efficientdata transmission at a low cost with a nominal peak throughput formulti-antennal communications.

Channel weight information and channel status information regardingevery mobile station, which are transmitted from the mobile stations tothe base station as feedback signals, are utilized. In addition, sincechannel investigation and tracking sections are separated in the presentinvention, so that the problem of delay in high-speed Dopplerenvironments can be solved.

Furthermore, packet fairness information regarding a plurality of mobilestations is considered in calculating maximum transmission channelcapacities, enabling selecting mobile stations for simultaneous datatransmission.

Mutual weight information generated through investigation and trackingsections is quantized, allowing efficient channel informationmeasurement. Generating channel information based on the channel weightinformation and channel status information regarding each of the mobilestations in the present invention ensures compatibility with existingstandard protocols.

While the present invention has been particularly shown and describedwith reference to exemplary embodiments thereof, it will be understoodby those of ordinary skill in the art that various changes in form anddetails may be made therein without departing from the spirit and scopeof the present invention as defined by the following claims.

1. A mobile station, comprising: at least one mobile station antenna,and the mobile station measuring downlink characteristics of multiplebase station/mobile station antenna channels based on pilot channelsignals transmitted from a base station, determining weight informationand channel status information based on the downlink characteristics,converting the determined weight information and channel statusinformation into feedback signals, transmitting the feedback signals tothe base station, and detecting High-Speed Downlink Shared CHannel(HS-DSCH) signals in units of a frame based on the downlinkcharacteristics, and a first control signal and data signals, which aretransmitted from the base station.
 2. The mobile station of claim 1,wherein the mobile station comprises: a channel characteristicsmeasurement unit that measures the downlink characteristics based on thepilot channel signals received through the mobile station antenna; achannel information determination unit that determines weightinformation and channel status information that maximizes transmissioncapacity based on the downlink characteristics, which are compressed tobe fed back; an information feedback unit that converts the weightinformation and channel status information received from the channelinformation determination unit into the feedback signals and transmitsthe feedback signals through the mobile station antennal to the basestation; a control information restoration unit that compensates for adistortion of the first control signal received from the base stationbased on the downlink characteristics and restores a second controlsignal from the distortion-compensated first control signal, the secondcontrol signal including information as to whether the data signals arefrom a desired basis matrix and information on the number of bitsincluded; a data information restoration unit that restores datainformation that is received from every basis from the data signalsreceived from the base station and the downlink characteristics; a datainformation selection unit that selects data information received fromthe desired basis matrix from among the data information received fromall of the basis matrices in response to the second control signal, andoutputs the selected data information; and a data informationcombination unit that combines the selected data information receivedfrom the data information selection unit and outputs the combinedresults as the High-Speed Downlink Shared CHannel (HS-DSCH) signals. 3.A method of mobile communications performed in a mobile station, themethod comprising: measuring downlink characteristics of multiple basestation/mobile station antenna channels based on pilot channel signalstransmitted from a base station; determining weight information andchannel status information based on the downlink characteristics;converting the determined weight information and channel statusinformation into the feedback signals; transmitting the feedback signalsto the base station; and detecting High-Speed Downlink Shared CHannel(HS-DSCH) signals in units of a frame based on the downlinkcharacteristics, and a first control signal and data signals, which aretransmitted from the base station.